UP TO 150 Australians could be involved in Syrian and Iraqi conflicts, as Foreign Minister Julie Bishop warned the government was now cancelling passports of those citizens it considered to now be terrorist threats.

Ms Bishop told the ABC Insiders program on Sunday she was "particularly concerned" about those Australians taking up a leadership role in radicalising others in the war torn countries.

"The fear is they will come back to Australia with these new-found abilities and talents in terrorism," she said.

Ms Bishop refused to say how many passports had been cancelled beyond "quite a few".

"It is deeply disturbing, that's why the Australian Government is taking this very seriously."

Ms Bishop said there were concerns Australians were involved with the Islamic State in Iraq and Syria or ISIS, that had been winning military gains in both Iraq and Syria since its creation in April last year.